Conventional buffer circuit includes multiple transistors, and is biased at a first voltage level +VDD and a second voltage level −VDD. In order to make these transistors fully turned on and fully turned off, all terminals of these transistors may be operated at the voltage levels between −VDD to +VDD. In this case, two terminals of some transistors may suffer the voltage difference more than the voltage level of VDD, causing the damage of the transistor. One way to avoid the electrical over-stress issue is to use the component which is capable of operating with high voltage supplies while being fabricated using a specific technology as a switch allows for larger voltage difference. However, this method results in increasing the overall cost of the buffer circuit. Therefore, it is a prominent task for the industry to solve the problem and provide a buffer circuit preventing from the electrical over-stress issue without the use of the high voltage component.